UPDATED: What’s the difference between a Water Quality Advisory and a Boil Water Notice?

Since flooding began last weekend, multiple water quality alerts have been issued in response to increased turbidity levels in drinking water for the Central Okanagan. There is a difference between a Water Quality Advisory and a Boil Water Notice, read on to find out why they are different.

The purpose of these alerts is to notify the public about potential threats to drinking water or to advise of changes in water quality that may present health risks.

Having many different water sources combined with several purveyors of water in the Central Okanagan confuses it a bit more. Some of the purveyors even have different water sources for their system, further complicating who gets what water and if the source needs an alert. To add to that, there are three types of alerts, a Water Quality Advisory, a Boil Water Notice and lastly a Do Not Use Notice.

We are going to do our best to make this more understandable.

First off, what are the types of alerts and how are they determined. Turbidity is the main method of testing water and determining if an alert is required. It is simply shining a light through a sample of water and measuring the amount of light that makes it through. A more scientific explanation is below.

What is turbidity?

Turbidity is a water quality term that refers to fine suspended particles of clay, silt, inorganic matter, plankton and other microscopic organisms that are picked up by water as it passes through a watershed.

Turbidity, which is measured and reported in nephelometric turbidity units (NTU), is an optical measurement of water’s ability to scatter and absorb light rather than transmit it in straight lines. Turbidity levels can range from less than 1 NTU to more than 1,000 NTU. At 5 NTU water is visibly cloudy; at 25 NTU it is murky.

Measuring Water Quality

Good quality water (<1 NTU) - No alert

Even when the water measures low turbidity levels, it is still recommended that newborns and people with compromised immune systems drink boiled water or a safe alternative if they are served by an unfiltered water source.

Fair quality water (1-5 NTU) - Water Quality Advisory

When turbidity levels are between 1-5 NTU, it is recommended that children, the elderly, people with compromised immune systems and anyone seeking additional protection drink boiled water or a safe alternative.

Poor quality water (>5 NTU) - Boil Water Notice

When turbidity levels surpass 5 NTU, all users should drink boiled water or a safe alternative like bottled water.

If you’re still a tad confused, watch this video below where a person explains how to measure turbidity in a given sample of water.

Types of Alerts

Based on turbidity levels the following alerts are issued.

A Water Quality Advisory is issued in situations in which the public health risk posed by the water supply system is modest or when the turbidity is between 1 - 5 NTU. When a Water Quality Advisory is issued, it is recommended that newborns and people with compromised immune systems drink boiled water or a safe alternative if they are served by an unfiltered water source.

A Boil Water Notice is issued when the threat to public health posed by the water supply system is significant and can be effectively addressed through boiling water. If a boil water notice is issued for a water system that you use, you should refrain from drinking tap water unless you first bring it to a rolling boil for at least one minute.

A Do Not Use Notice is typically used when known contaminants are found in the water source.

Within West Kelowna there are several systems. Pritchard and Sunnyside are on a Water Quality Advisory, The Lakeview and the West Kelowna Estates systems are currently not on any alerts.

The City of West Kelowna has provided an interactive map for users of water systems that are currently under Water Quality Advisories, helping to simplify identification of properties within advisory areas. Currently, approximately 2,150 water customers in West Kelowna are under Water Quality Advisory. The West Kelowna Estates (1,000 connections), Sunnyside (1,000 connections) and Pritchard (150 connections) Water Systems, which pull water from Okanagan Lake, are experiencing increased turbidity due to spring runoff and flooding activity. These unfiltered systems are treated with chlorination only. The City will continue to monitor these systems and will advise customers when the Water Quality Advisory is lifted.

The interactive map is available on the City’s website, www.westkelownacity.ca/water. Users are encouraged to sign up for e-Notification on the City’s website, at www.westkelownacity.ca/notifyme to have updates automatically emailed directly to them.